The city streets are teeming with thousands of mentally ill homeless people capable of psychotic acts of random violence if left untreated, experts warned yesterday.

As many as 11,000 of the city’s 33,000 homeless adults have some form of mental illness, said D.J. Jaffe, executive director of the Mental Illness Policy Organization.

Of that number, about 3,300 are potentially violent, Jaffe said.

“When untreated, they’re capable of horrific acts,” said Jaffe. “The danger is that they’re so sick that they don’t know they’re sick, and their brain is incapable of regulating their own behavior.”

He urged New Yorkers to be especially wary of people screaming at voices only they can hear, wearing tons of clothes in the summer or eating out of trash cans.

“But if you’re walking down the street, you know who’s mentally ill — it doesn’t take a nuclear scientist.”

Jaffe said steps must be taken to strengthen Kendra’s Law — a loophole-ridden 1999 measure intended to allow courts to forcibly treat the dangerously unhinged.

“We want mandatory evaluations of all mentally ill who are being released from jails, prisons or involuntary hospitalizations,” he said.

Even Andrew Goldstein, the schizophrenic man who shoved Kendra Webdale to her death in front of a train in 1999, is calling for tougher laws — to keep nuts like himself off the street.

“There should be stricter regulations,” he told The Post in his first-ever jailhouse interview.

The city’s Department of Homeless Services disputed Jaffe’s figures but characterized the number of mentally ill homeless who do not use its shelter system as “significant.”

“If people feel that there is someone in the street that’s dangerous, they need to call 911,” said spokeswoman Barbara Brancaccio.

“The administration has invested unprecedented sums in street outreach to bring those individuals into settings where they can receive the treatment and services they need,” she added.

Critics said the city is to blame for the homeless epidemic — for failing to provide permanent supportive housing for a ballooning homeless population.

“This is the highest homeless population in the city’s history,” said Patrick Markee, a senior policy analyst with the Coalition for the Homeless who noted that when Mayor Bloomberg first took office the number of homeless was about 31,000.